This invention relates to an integrated pump and ceramic valve apparatus for pumping discrete liquid volumes to points of use of the liquid volumes. More particularly, this invention relates to an integrated displacement pump and ceramic valve for pumping discrete liquid volumes to points of use.
At the present time, discrete liquid volumes are pumped with a syringe pump comprising a barrel, a face seal which moves within the barrel and a reciprocating plunger attached to the face seal. The syringe pump includes a valve construction formed of a polymeric composition which directs the pumped liquid volumes to a point of use. The valve construction includes a housing having a hollow, essentially conical interior surface into which is press fit a mating, essentially conical rotor. The rotor is provided with fluid passageways that control flow of liquid into the syringe pump and flow of liquid from the syringe pump while providing sealing between a pump inlet and a pump outlet. Since organic solvents and diluents are sometimes used to form the liquid being pumped such as dimethylsulfoxide (DMSO) or tetrahydrofuran (THF), the valve rotor commonly swells which causes it to deteriorate. Also, the use of the conically shaped seal limits the pressure at which the liquid is pumped while retaining desired sealing since higher pressures increase the difficulty in rotating the valve rotor. Operating pressures are also limited due to the use of polymeric materials in the valve such as polytetrafluoroethylene (PTFE) which tend to cold flow at elevated pressures.
While the available syringe pumps have been useful for their intended purpose, they also have disadvantages. In order to attain a tight fit between the barrel and the face seal, the manufacturing of both the barrel and face seal must be made at tight tolerances. In addition, when utilizing the most commonly used materials comprising a glass barrel and a (PTFE) face seal, undesirable shedding of the PTFE occurs which contaminates the liquid being pumped. Furthermore, a tight fit between the barrel and face seal results in chattering of the face seal during its movement within the barrel. This leads to a loss of control of the liquid volume being pumped. In addition, the average useful life of presently available syringe pumps is only about 10 to about 100,000 cycles.
An additional problem encountered in presently available pumps is residue buildup at the pump seals which reduce useful pump life. While it may be possible to supply wash water to the pump seal to reduce residual build up, such an arrangement would require a separate motor to activate a pump for the wash water.
Accordingly, it would be desirable to provide a pump apparatus capable of delivering discrete liquid volumes to a point of use such as different areas of a sample tray in a maimer which is repeatable for long time periods of 1,000,000 cycles or more. In addition, it would be desirable to provide such a pump apparatus which avoids shedding of polymeric particles during pumping. Furthermore, it would be desirable to provide such a pump wherein internal seals can be cleaned periodically or continuously without the need for a motor in addition to the motor for the pump apparatus.